[jira] [Commented] (TS-758) HostDB fails to insert RR entries (allocation fails) claiming DB is full

["Alan M. Carroll (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082728#comment-13082728 ] 

Alan M. Carroll commented on TS-758:
------------------------------------

This appears to be a result of HostDB running out of space in the host storage, rather than exceeding the number of hosts. Because HostDB uses hash tables internally it must commit to a fixed number of hosts when the DB is initialized (that's set by hostdb.size). The memory footprint, however, is determined by how many entries are returned by DNS servers for the hosts in the table. This can vary quite a bit so one can run out of memory without exceeding the maximum host count. For those who remember "the inode problem" this is basically the same thing.

Currently I have classify this as "not a bug". The behavior is as intended. The best response is to increase the value in proxy.config.hostdb.storage_size. Presumably this was original done to provide tuning opportunities while minimizing resource usage. With modern system I recommend just bumping the value up by 50% or so if you see this in the log.

Longer term, the HostDB storage should be rewritten to be more dynamic but that is definitely a long term prospect.


> HostDB fails to insert RR entries (allocation fails) claiming DB is full
> ------------------------------------------------------------------------
>
>                 Key: TS-758
>                 URL: https://issues.apache.org/jira/browse/TS-758
>             Project: Traffic Server
>          Issue Type: Bug
>          Components: DNS
>    Affects Versions: 2.1.8
>            Reporter: Leif Hedstrom
>             Fix For: 3.1.1
>
>
> After running in forward proxy for a few days, I got a bunch of these errors:
> [May  3 17:13:11.574] Server {140488838387680} WARNING: out of room in hostdb for round-robin DNS data
> [May  3 17:13:11.726] Server {140488838387680} WARNING: out of room in hostdb for round-robin DNS data
> [May  3 17:13:11.736] Server {140488838387680} WARNING: out of room in hostdb for round-robin DNS data
> [May  3 17:13:14.072] Server {140488821982992} WARNING: out of room in hostdb for round-robin DNS data
> [May  3 17:13:17.114] Server {140488838387680} WARNING: out of room in hostdb for round-robin DNS data
> I'm not sure why it thinks it's out of room, there is no way I've filled my hostdb cache (I'm fairly certain). I'm not able to reproduce the problem (easily).

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